PECA's Return Impairments Unit (Unit 7) is a subsection of PECA's Transmission Medium Impairment Simulator (TMIS) systems.

The TMIS Return Impairments unit provides the means to select and inject individual or multiple additive impairments into the Return (Upstream) test carrier path.  The Forward Impairments unit is capable of selecting and controlling six impairments.  

Typical Forward Impairments are:

• Broadband Noise                              0.1 dB step attenuation resolution

• Carrierwave Interference (CW)       1.0 dB step attenuation resolution

• Noise/CW Impulse Noise                1.0 dB step attenuation resolution

• CPD (Common Path Distortion)     1.0 dB step attenuation resolution

• EXPAN 1                                           1.0 dB step attenuation resolution

• EXPAN 2                                           1.0 dB step attenuation resolution

The Return Impairments Unit can be controlled either manually, via front panel controls or via RS-485 interface for computer and automated control.

The computer (automated) control is via four I/O boards which are internal to the Return Impairments unit and four PECA RS-485 SmartPlug Modules externally connected to the 25 pin D connectors on the I/O boards.

In a fully integrated test system, the PECA RS-485 SmartPlug Modules are daisy chained via RJ-11 modular cables between units. The chain is connected to an RS-232 to RS-485 converter on the RS-232 COM port of a PC or via PECA Unit 10.